Control device for plurality of rotating electrical machines

Abstract

A control device for a rotating electrical machine system having a plurality of rotating electrical machines is provided with a single current control circuit and a controller. The controller sets an operating point of at least one rotating electrical machine of the plurality of rotating electrical machines, and sets the current for each rotating electrical machine so that one of the efficiency of the current control circuit and the overall efficiency with respect to all the rotating electrical machines. The controller controls the current control circuit so that the current control circuit supplies a composite current to all rotating electrical machines, the composite current combining the set current for each rotating electrical machine.

What is claimed is:  
     
       1. A control device for a rotating electrical machine system having a first rotating electrical machine and a second rotating electrical machine, the rotation of each rotating electrical machine being controlled by a current flowing in response to the rotational phase of a rotor thereof, the control device comprising: 
       a single current control circuit which is connected to the first and second rotating electrical machines and produces a composite current comprising the current for each rotating electrical machine; and  
       a controller functioning to:  
       set an operating point of the first rotating electrical machine,  
       set an operating point of the second rotating electrical machine in response to the set operating point of the first rotating electrical machine so that one of the efficiency of the current control circuit and the overall efficiency is maximized, wherein the overall efficiency is the product of the efficiency of the current control circuit, the efficiency of the first rotating electrical machine, and the efficiency of the second rotating electrical machine,  
       set the current for each rotating electrical machine based on the set operating points of the first and second rotating electrical machines, so as to minimize the current average value of the composite current while maintaining the set operating points of the first and second rotating electrical machines, and  
       control the current control circuit so that the current control circuit produces the composite current for all the first and second rotating electrical machines.  
     
     
       2. The control device as defined by  claim 1 , wherein the operating point of the first rotating electrical machine and the operating point of the second rotating electrical machine comprise a set of a rotational angular velocity and torque. 
     
     
       3. The control device as defined by  claim 1 , wherein the controller functions to set d-axis and g-axis currents for each rotating electrical machine based on the set operating points of the first and second rotating electrical machines so as to minimize an evaluation function corresponding to the current average value of the composite current, the evaluation function being a function of a peak value of the current for each rotating electrical machine. 
     
     
       4. The control device as defined by  claim 1 , wherein the first and second rotating electrical machines comprises a generator connected to an engine and an electric motor, and wherein power generated by the generator is supplied to the electric motor. 
     
     
       5. The control device for a rotating electrical machine as defined by  claim 4 , wherein the controller stores a four-dimensional map for setting the overall efficiency based on both the operating point of the electric motor and the operating point of the generator, and sets the generator operating point which maximizes the overall efficiency by looking up the four-dimensional map. 
     
     
       6. The control device as defined by  claim 5 , wherein the four-dimensional map is generated by: 
       determining an operating point for the electric motor and an operating point for the generator,  
       determining a minimum value for the current average value of the composite current based on the determined operating point for the electric motor and the determined operating point for the generator,  
       calculating an efficiency of the single current control circuit based on the minimum value which is taken when the current average value of the composite current takes the minimum value,  
       calculating an efficiency of the generator and an efficiency of the electric motor, not including the loss of the single current control circuit, which are taken when the current average value of the composite current takes the minimum value,  
       calculating a value representing an overall efficiency from the product of the calculated efficiency of the generator, the calculated efficiency of the electric motor and the calculated efficiency of the single current control circuit, and  
       storing a data set of the determined operating point of the electric motor, the determined operating point of the generator and the calculated value representing an overall efficiency.  
     
     
       7. The control device for a rotating electrical machine as defined by  claim 5 , 
       wherein the four-dimensional map comprises a combination of a first two-dimensional map representing the operating points of the electric motor for each of which a second two dimensional map of overall efficiency is provided, and the second two dimensional map for setting an overall efficiency from an operating point of the generator,  
       wherein the controller selects the second two-dimensional map corresponding to the operating point of the electric motor by looking up the first two-dimensional map based on the operating point of the electric motor, and  
       wherein the controller sets an operating point for the generator so that the overall efficiency is maximized, by looking up the second two-dimensional map based on the operating point of the generator.  
     
     
       8. The control device as defined by  claim 1 , wherein the rotating electrical machine system is mounted in a hybrid vehicle, and the first and second rotating electrical machines comprise a generator connected to an engine and an electric motor connected to the drive shaft of the vehicle; and one of the rotating electrical machines is the electric motor and the other rotating electrical machine is the generator, and the operating point of the electric motor is set in response to a speed of the vehicle and an accelerator position of the hybrid vehicle. 
     
     
       9. The control device as defined by  claim 4 , wherein the controller sets a current for each rotating electrical machine so that the current average value for the composite current is minimized only in a condition in which the maximum engine torque is greater than the torque of the generator. 
     
     
       10. The control device as defined by  claim 4 , wherein the controller functions to: 
       determine an operating point of the generator at which optimal engine fuel economy is attained,  
       determine an operating point of the generator at which the current average value of the composite current is minimized, and  
       set the current for each rotating electrical machine based on the two determined operating points of the generator.  
     
     
       11. A control method for a rotating electrical machine system having a first rotating electrical machine and a second rotating electrical machine, the rotation of each rotating electrical machine being controlled by a current flowing in response to the rotational phase of a rotor thereof, and having a single current control circuit which is connected to the first and second rotating electrical machines and produces a composite current comprising the current for each rotating electrical machine, the control method comprising: 
       setting an operating point of the first rotating electrical machine;  
       setting an operating point of the second rotating electrical machine in response to the set operating point of the first rotating electrical machine so that one of the efficiency of the current control circuit and the overall efficiency is maximized, wherein the overall efficiency is the product of the efficiency of the current control circuit, the efficiency of the first rotating electrical machine, and the efficiency of the second rotating electrical machine;  
       setting the current for each rotating electrical machine based on the set operating points of the first and second rotating electrical machines so as to minimize the current average value of the composite current while maintaining the set operating points of the first and second rotating electrical machines; and  
       controlling the current control circuit so that the current control circuit produces the composite current for the first and second rotating electrical machines.  
     
     
       12. A control device for a rotating electrical machine system having a first rotating electrical machine and a second rotating electrical machines, the rotation of each rotating electrical machine being controlled by a current flowing in response to the rotational phase of a rotor thereof, the control device comprising: 
       a single current control circuit which is connected to the first and second rotating electrical machines and produces a composite current comprising the current for each rotating electrical machine;  
       means for setting an operating point of the first rotating electrical machine;  
       means for setting an operating point of the second rotating electrical machine in response to the set operating point of the first rotating electrical machine so that one of the efficiency of the current control circuit and the overall efficiency is maximized, wherein the overall efficiency is the product of the efficiency of the current control circuit, the efficiency of the first rotating electrical machine, and the efficiency of the second rotating electrical machine;  
       means for setting the current for each rotating electrical machine based on the set operating points of the first and second rotating electrical machines; and  
       means for controlling the current control circuit to produce the composite current for the first and second rotating electrical machines, wherein the current average value of the composite current is minimized while maintaining the set operating points of the first and second rotating electrical machines.